The present invention relates to a double shaft supporting construction for an automotive automatic transmission.
There is known, for example, a construction as shown in FIG. 1 as a conventional double shaft supporting construction for an automotive automatic transmission. In FIG. 1, a gear 4 is integrally formed at an end portion of an inner shaft 2, and the gear 4 meshes with a gear 6. An outer shaft 8 is rotationally supported on the inner shaft 2 via a needle bearing 10. A gear 12 is integrally formed at the vicinity of an end portion of the outer shaft 8. A ball bearing is interposed between the end portion of the outer shaft 8 and a case 16.
In this double shaft supporting construction, a load inputted from the gear is inputted into the outer shaft 8 via the needle bearing 10 and is further borne by the case 16 via the ball bearing 14.
In this supporting construction, however, since a torsional bending as well as a bending load are inputted into the inner shaft 2 by virtue of a reaction force from the power transmission gear 4 and furthermore a shaft diameter which can bear the both loads is needed, there is caused a problem that the diameter and weight of the inner shaft are increased.
In addition, since the construction is such that the bending load borne by received by the gear 4 is borne by the needle bearing 10 and the ball bearing 14 via the inner shaft 2, a certain magnitude of strength is required for the inner shaft 2, this leading to a problem that the diameter of the inner shaft 2 is increased.
FIG. 2 shows another conventional example of a double shaft supporting construction for an automotive automatic transmission. In this double shaft supporting construction, an inner shaft 2 is supported in a case 16 via a roller bearing 18, and an outer shaft 8 is supported in the case via a ball bearing 14.
In this double shaft supporting construction, too, however, as in the case with the supporting construction shown in FIG. 1, a bending load and a torsional load are inputted into the inner shaft 2 due to a reaction force from a power transmission gear 4, and since a shaft diameter that can bear the both loads is needed, there is also caused the problem that the diameter and weight of the inner shaft 2 are increased.
[Patent Literature No. 1]
JP-A-2001-323973